//The MIT License

//Copyright (c) 2009 Lluis Sanchez, Nick Darnell

//Permission is hereby granted, free of charge, to any person obtaining a copy
//of this software and associated documentation files (the "Software"), to deal
//in the Software without restriction, including without limitation the rights
//to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//copies of the Software, and to permit persons to whom the Software is
//furnished to do so, subject to the following conditions:

//The above copyright notice and this permission notice shall be included in
//all copies or substantial portions of the Software.

//THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//THE SOFTWARE.

using System;
using System.Reflection.Emit;

namespace Polymorph
{
    public class CodeWhen : CodeExpression
    {
        CodeExpression condition;
        CodeExpression trueBlock;
        CodeExpression falseBlock;

        public CodeWhen(CodeExpression condition, CodeExpression trueResult, CodeExpression falseResult)
        {
            this.condition = condition;
            if (condition.ResultType != typeof(bool))
                throw new InvalidOperationException("Condition expression is not boolean");
            if (trueResult.ResultType != falseResult.ResultType)
                throw new InvalidOperationException("The types of the true and false expressions must be the same");
            trueBlock = trueResult;
            falseBlock = falseResult;
        }

        public override void Generate(ILGenerator gen)
        {
            Label falseLabel = gen.DefineLabel();
            Label endLabel = gen.DefineLabel();

            GenerateCondition(gen, falseLabel);
            trueBlock.Generate(gen);
            gen.Emit(OpCodes.Br, endLabel);
            gen.MarkLabel(falseLabel);
            falseBlock.Generate(gen);

            gen.MarkLabel(endLabel);
        }

        void GenerateCondition(ILGenerator gen, Label falseLabel)
        {
            if (condition is CodeConditionExpression)
                ((CodeConditionExpression)condition).GenerateForBranch(gen, falseLabel, false);
            else
            {
                condition.Generate(gen);
                gen.Emit(OpCodes.Brfalse, falseLabel);
            }
        }

        public override void PrintCode(CodeWriter cp)
        {
            cp.Write("(");
            condition.PrintCode(cp);
            cp.Write(") ? ");
            trueBlock.PrintCode(cp);
            cp.Write(" : ");
            falseBlock.PrintCode(cp);
        }

        public override Type ResultType
        {
            get { return trueBlock.ResultType; }
        }
    }
}